The iliac fossa is a large, smooth, concave surface on the internal surface of the ilium (part of the 3 fused bones making the hip bone). The fossa is bounded above by the iliac crest, and below by the arcuate line; in front and behind, by the anterior and posterior borders.

The fossa gives origin to the Iliacus muscle and is perforated at its inner part by a nutrient canal; below this there is a smooth, rounded border, the arcuate line, which runs anterior, inferior, and medial.